Date:   Sun, 18 Mar 2018 11:54:22 +0100
From:   jacopo mondi <jacopo@...ndi.org>
To:     John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [RFC 2/4] sh: ecovec24: conditionally register backlight device

Hi Andrian,

On Sat, Mar 17, 2018 at 07:21:17PM +0900, John Paul Adrian Glaubitz wrote:
>
>
> > On Mar 17, 2018, at 6:25 PM, jacopo mondi <jacopo@...ndi.org> wrote:
> >
> > Hi Dmitry,
> >
> >> On Fri, Mar 16, 2018 at 04:38:00PM -0700, Dmitry Torokhov wrote:
> >> Hi Jacopo,
> >>
> >>> On Fri, Mar 16, 2018 at 11:07:48AM +0100, jacopo mondi wrote:
> >>> Hello Dmitry
> >>>
> >>> FYI I am brushing the ecovec board these days as well
> >>> https://www.spinics.net/lists/linux-sh/msg52536.html
> >>>
> >>
> >> What is the ecovec board BTW? Is it some devkit or what? It seems quite
> >> old to me.
> >
> > Yes, it is a SuperH 4 based development board. It is old for sure. I'm
> > also working on removing some stuff the ecovec board file is the only
> > user of...
>
> Umh, but I’m still using the SH7724 Evovec board. Please don’t remove support for that.
>
> The SuperH port of the Linux kernel is still maintained.

Sorry if I was not clear here, it is not anyone's intention to remove any
support for any SH board. The media subsystem is working to replace
some components (the legacy camera drivers) a few SH boards (ecovec
included) are the only remaining user of. Nobody is working to remove
support for those boards.

I have access to a few SH boards, if you're planning to collect that
informations in some wiki, I'll list myself there.

Thanks
   j

>
> Adrian
>
> >
> >>> And I have a board to test with but without any display panel, I'm
> >>> afraid.
> >>>
> >>>> On Thu, Mar 15, 2018 at 03:42:00PM -0700, Dmitry Torokhov wrote:
> >>>> Commit fe79f919f47e ("sh: ecovec24: Use gpio-backlight") removed custom
> >>>> backlight support and switched over to generic gpio-backlight driver. The
> >>>> comment when we run with DVI states "no backlight", but setting
> >>>> gpio_backlight_data.fbdev to NULL actually makes gpio-backlight to react to
> >>>> events from any framebuffer device, not ignore them.
> >>>>
> >>>> We want to get rid of platform data in favor of generic device properties
> >>>> in gpio_backlight driver, so we can not have kernel pointers passed around
> >>>> to tie the framebuffer device to backlight. Assuming that the intent of the
> >>>> above referenced commit was to indeed not export backlight when using DVI,
> >>>> let's switch to conditionally registering backlight device so it is not
> >>>> present at all in DVI case.
> >>>>
> >>>> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> >>>> ---
> >>>> arch/sh/boards/mach-ecovec24/setup.c | 24 +++++++++++++++++-------
> >>>> 1 file changed, 17 insertions(+), 7 deletions(-)
> >>>>
> >>>> diff --git a/arch/sh/boards/mach-ecovec24/setup.c b/arch/sh/boards/mach-ecovec24/setup.c
> >>>> index 6f929abe0b50f..67633d2d42390 100644
> >>>> --- a/arch/sh/boards/mach-ecovec24/setup.c
> >>>> +++ b/arch/sh/boards/mach-ecovec24/setup.c
> >>>> @@ -368,7 +368,6 @@ static struct platform_device lcdc_device = {
> >>>> };
> >>>>
> >>>> static struct gpio_backlight_platform_data gpio_backlight_data = {
> >>>> -    .fbdev = &lcdc_device.dev,
> >>>>    .gpio = GPIO_PTR1,
> >>>>    .def_value = 1,
> >>>>    .name = "backlight",
> >>>> @@ -987,7 +986,6 @@ static struct platform_device *ecovec_devices[] __initdata = {
> >>>>    &usb1_common_device,
> >>>>    &usbhs_device,
> >>>>    &lcdc_device,
> >>>> -    &gpio_backlight_device,
> >>>>    &ceu0_device,
> >>>>    &ceu1_device,
> >>>>    &keysc_device,
> >>>> @@ -1077,6 +1075,8 @@ static int __init arch_setup(void)
> >>>> {
> >>>>    struct clk *clk;
> >>>>    bool cn12_enabled = false;
> >>>> +    bool use_backlight = false;
> >>>> +    int error;
> >>>>
> >>>>    /* register board specific self-refresh code */
> >>>>    sh_mobile_register_self_refresh(SUSP_SH_STANDBY | SUSP_SH_SF |
> >>>> @@ -1193,9 +1193,6 @@ static int __init arch_setup(void)
> >>>>        lcdc_info.ch[0].lcd_modes        = ecovec_dvi_modes;
> >>>>        lcdc_info.ch[0].num_modes        = ARRAY_SIZE(ecovec_dvi_modes);
> >>>>
> >>>> -        /* No backlight */
> >>>> -        gpio_backlight_data.fbdev = NULL;
> >>>> -
> >>>>        gpio_set_value(GPIO_PTA2, 1);
> >>>>        gpio_set_value(GPIO_PTU1, 1);
> >>>>    } else {
> >>>> @@ -1217,6 +1214,8 @@ static int __init arch_setup(void)
> >>>>        /* enable TouchScreen */
> >>>>        i2c_register_board_info(0, &ts_i2c_clients, 1);
> >>>>        irq_set_irq_type(IRQ0, IRQ_TYPE_LEVEL_LOW);
> >>>> +
> >>>> +        use_backlight = true;
> >>>>    }
> >>>>
> >>>>    /* enable CEU0 */
> >>>> @@ -1431,8 +1430,19 @@ static int __init arch_setup(void)
> >>>>    gpio_set_value(GPIO_PTG4, 1);
> >>>> #endif
> >>>>
> >>>> -    return platform_add_devices(ecovec_devices,
> >>>> -                    ARRAY_SIZE(ecovec_devices));
> >>>> +    error = platform_add_devices(ecovec_devices,
> >>>> +                      ARRAY_SIZE(ecovec_devices));
> >>>
> >>> I would invert this.
> >>> Register the backlight first, then all other devices.
> >>
> >> We could do that, but why would that be better?
> >>
> >
> > That if backlight device registration fails we do not register all
> > other devices. But yes that may be a bit too harsh, isn't it?
> >
> >>>
> >>>
> >>>> +    if (error)
> >>>> +        return error;
> >>>> +
> >>>> +    if (use_backlight) {
> >>>> +        error = platform_device_add(&gpio_backlight_device);
> >>>> +        if (error)
> >>>> +            pr_warn("%s: failed to register backlight: %d\n",
> >>>> +                error);
> >>>
> >>> Could you use dev_warn here? Also the format is wrong, I assume you
> >>
> >> I would rather not, as the backlight device would be in unknown state
> >> here, and using dev_warn with device that has not been fully registered
> >> does not give any benefits. There is also no ambiguity as there is only
> >> one backlight.
> >
> > You are very correct, sorry for the fuss.
> >
> >>
> >>> are missing a '__func__' as second function argument.
> >>
> >> I'll fix this.
> >>
> >>>
> >>> Also, you may want to return error.
> >>
> >> How would caller handle this error? Should we kill all successfully
> >> registered devices on error adding backlight?
> >
> > As the function returned an error code for 'platform_add_devices()' I
> > thought we may want to return one as well. That's why I proposed to
> > invert the registration order :)
> >
> > All minor nits btw,  sorry for jumping up, I understand this is an
> > RFC and ecovec board file is not the real juice of this series ;)
> >
> > Ping me if I can help with testing as I've the board.
> >
> > Thanks
> >   j
> >
> >>
> >> Thanks.
> >>
> >> --
> >> Dmitry
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-sh" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

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